全文获取类型
收费全文 | 25930篇 |
免费 | 277篇 |
国内免费 | 243篇 |
专业分类
安全科学 | 762篇 |
废物处理 | 1107篇 |
环保管理 | 3497篇 |
综合类 | 3403篇 |
基础理论 | 6984篇 |
环境理论 | 6篇 |
污染及防治 | 7398篇 |
评价与监测 | 1715篇 |
社会与环境 | 1408篇 |
灾害及防治 | 170篇 |
出版年
2022年 | 212篇 |
2021年 | 215篇 |
2020年 | 152篇 |
2019年 | 195篇 |
2018年 | 367篇 |
2017年 | 353篇 |
2016年 | 588篇 |
2015年 | 453篇 |
2014年 | 692篇 |
2013年 | 2174篇 |
2012年 | 828篇 |
2011年 | 1118篇 |
2010年 | 888篇 |
2009年 | 1021篇 |
2008年 | 1200篇 |
2007年 | 1239篇 |
2006年 | 1095篇 |
2005年 | 920篇 |
2004年 | 908篇 |
2003年 | 921篇 |
2002年 | 864篇 |
2001年 | 1141篇 |
2000年 | 812篇 |
1999年 | 465篇 |
1998年 | 350篇 |
1997年 | 332篇 |
1996年 | 376篇 |
1995年 | 403篇 |
1994年 | 354篇 |
1993年 | 313篇 |
1992年 | 304篇 |
1991年 | 274篇 |
1990年 | 313篇 |
1989年 | 299篇 |
1988年 | 254篇 |
1987年 | 242篇 |
1986年 | 202篇 |
1985年 | 221篇 |
1984年 | 250篇 |
1983年 | 248篇 |
1982年 | 237篇 |
1981年 | 222篇 |
1980年 | 188篇 |
1979年 | 214篇 |
1978年 | 145篇 |
1977年 | 145篇 |
1976年 | 128篇 |
1975年 | 141篇 |
1973年 | 133篇 |
1972年 | 133篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
983.
984.
Sylvie Gagnon William Fraser Dr Bertrand Fouquette Adrien Bastide Marc Bureau Jean-Yves Fontaine Céline Huot 《黑龙江环境通报》1992,12(1):9-18
During a 7-year period, 117 fetal karyotypes were available from 131 genetic amniocenteses. These procedures were performed between 14 and 37 weeks' gestation for the following abnormal ultrasound findings: (1) intrauterine growth retardation (IUGR)—61 cases; (2) fetal malformation—71 cases; and (3) amniotic fluid volume (AFV) abnormality—60 cases. Chromosomal abnormalities were identified in 19 cases (16.2 per cent). Aneuploidy was 2.5 times as frequent in the presence of malformations than in their absence. No correlation was demonstrated between specific fetal malformations and specific chromosomal abnormalities. Aneuploidy was also twice as frequent in the presence of symmetrical IUGR than in its absence. No chromosomal abnormalities were found among eight cases of asymmetrical IUGR. Four cases of aneuploidy presented with isolated IUGR, three of these involving the X chromosome. The frequency of aneuploidy was the same with or without abnormalities of AFV (14.3 versus 16.4 per cent). No chromosomal abnormality was found associated with isolated AFV abnormalities. 相似文献
985.
The most common mutation in alpha-1-antitrypsin deficiency, conversion of a G to an A at base 9989 (PI-Z), was detected with the chemical cleavage of mismatch method, demonstrating the power of the method for prenatal diagnosis. Exon V of the gene was amplified using the polymerase chain reaction and heteroduplexes were formed to test for the presence of the mutation. The predicted C mismatch was readily detectable with hydroxylamine, and by making the probe from the chorionic villus sample it was possible to determine that the fetus was heterozygous, not homozygous, for the mutation. 相似文献
986.
987.
采用低温等离子体和絮凝剂协同处理印染废水.结果表明,染料废水脱色率和COD去除率随输入电压增大和放电时间延长而增加;电极间距、废水初始浓度、通入空气流量等因素对印染废水处理效果也有很大影响;气相中放电效果优于液相中放电,阳极电极在液面以上8mm左右时放电效果最好,在其他条件不变情况下随废水初始浓度和通入空气流量增大废水脱色和COD脱除率先增大再减小,有一最佳峰值.印染废水先经过等离子体处理后再加入絮凝剂处理效果优于先加絮凝剂后放电、仅有等离子体放电的过程.在本实验中初始浓度200mg/L(CODCr初始值572)印染废水在外加电压40kV、放电时间20min、电极间距8mm、通入空气流量16L/h条件下,与絮凝剂PAC相互协同作用可达到96%脱色率、63%COD去除率. 相似文献
988.
Hepatitis A virus (HAV) is currently recognized as an important human food borne pathogen, and it is one of the most resistant
enteric RNA viruses, is highly infectious, and may lead to widespread outbreaks. The aim of this study was to optimize the
methods to detect HAV from artificially contaminated food. To this end, strawberry and lettuce were experimentally contaminated
with HAV suspension containing 6 × 106 copies/ml. After contamination, HAV persistence and washing procedure were evaluated at 0, 1, 3, 7, and 9 days of storage.
Five elution buffers (PBS (pH 7.4)/0.1% Tween80; 50 mM glycine/3% (wt/vol) beef extract (pH 9.5); PBS (pH 7, 4); 25 mM glycine/0.1
Tween80; and 1 M sodium bicarbonate) were used to elute the virus, and qualitative and quantitative PCR were used for HAV
detection. HAV was detected by qualitative and quantitative PCR using any of the five elution buffers, but PBS was the most
effective. Even after washing, HAV was detected up to 9 days after contamination by quantitative PCR. Quantitative PCR was
more sensitive than qualitative PCR since samples containing viral load lower than 1.4 × 103 copies/ml could not be detected by qualitative PCR. Quantitative PCR can be used for rapid detection of food borne viruses
and will help in the monitoring and control of food borne disease. 相似文献
989.
A. Carvalho A. Monteiro S. Solman A.I. Miranda C. Borrego 《Environmental Science & Policy》2010,13(6):445-458
Climate change alone may deeply impact air quality levels in the atmosphere because the changes in the meteorological conditions will induce changes on the transport, dispersion and transformation of air pollutants. The aim of this work was to evaluate the impact of climate change on the air quality over Europe and Portugal, using a reference year (year 1990) and a IPCC SRES A2 year (year 2100). The Hadley Centre global atmospheric circulation model (HadAM3P) was used to provide results for these two climatic scenarios, which were then used as synoptic forcing for the MM5-CHIMERE air quality modelling system. In order to assess the contribution of future climate change on O3 and PM concentrations, no changes in regional emissions were assumed and only climate change forcing was considered. The modelling results suggest that the O3 monthly mean levels in the atmosphere may increase almost 50 μg m?3 across Europe in July under the IPCC SRES A2 scenario. In Portugal, this increase may reach 20 μg m?3. The changes of PM10 monthly average values over Europe will depend on the region. The increase in PM10 concentrations during specific months could be explained by the average reduction of the boundary layer height and wind speed. 相似文献
990.
A field study was conducted to evaluate the protozoan colonization patterns on artificial substrates in relation to organic pollution within a tropical harbour. The composition of protozoans and their succession rates on artificial substrates(polyurethane foam units) were compared between two field stations(A and B), and their presence were considered with regards to the prevailing water quality conditions at the study sites. Altogether 44 genera of flagellates and ciliates were documented. The common genera of flagellates encountered included Monas, Polytoma, and Chromalina. Among the ciliates, the predominant genera were Tetrahymena, Vorticella, Lagymophyra, and Heloiphyra. These groups exhibited characteristic successional patterns in relation to ambient water quality. At Station A, located close to the sewage outfall, the water quality parameters included poor Secchi-disc transparency(0.48 m), dissolved oxygen of 1.93 mg/ml, salinity of 18 psu, and temperature 31.3 degrees C. Here, the nanoflagellates (spumella) colonized first, followed by microcilliate(Tetrahymena) and sessile form(Vorticella). Station B, located on the seaward side, was characterized by relatively less-stressed environmental conditions with transparency 1.85 m and dissolved oxygen value of 6.04 mg/ml. Salinity of 27.27 psu, and mean temperature of 30 degrees C were recorded at "B". At this station, the nanoflagellate Polytoma was first documented to colonize on the substrates, followed by microcilliate(Lagynophrya) and suctorid(Heliophyra). These findings support the use of protozoans as indicator species for evaluating the hazards posed by organic pollution to natural estuarine communities. 相似文献